A tool holder for a manipulator is known which comprises a tool shaft extending along and rotatable about a main axis and having a tool-shaft end provided with a pivot defining a transverse axis. A tool is carried on the pivot and is displaceable relative to the tool shaft about the transverse axis. A support adjacent the tool carries one of a pair of mutually engageable conductors, the other of which is fixed on the tool-shaft end so as to be movable therewith. An electrical feed line is connected to the conductor fixed to the support and means including an electrical line is connected between the other conductor and the tool for feeding electricity through to the tool.
It is known from German patent document 2,416,536 to use a semicylindrical contact shoe centered on the main axis and surrounded by angularly extending flexible commutators which are tensioned radially in against an outer surface of the contact shoe. It is also known from U.S. Pat. No. 2,879,490 to employ a pair of contact shoes that are biased radially inwardly against a cylindrical outer conductor surface by powerful radially extending screws. Another system seen in U.S. Pat. No. 2,341,459 has two relatively rotatable conductors with axially confronting and abutting faces which are biased axially together by springs and the force of a pneumatic cylinder to form a good electrical connection.
In addition it is frequently desired to make fluid connections to the tool, which frequently itself has to be cooled, or to a fluid cylinder in the tool for minor displacements of the tool. This is particularly the case with tong-type pinch welders and the like. As the tool is frequently rotated a full 360.degree. to make an annular weld seam, it is necessary to provide complex fluid lines. These even further complicate the problem of conducting electricity through the holder.